Cougsfan

Once every couple thousand miles or so, my 47 re transmission decides to act up. It either doesn't shift into high gear at all, or it bounces back and forth between gears at any speed above 45 mph. This goes on for maybe 25 to a hundred miles or so, then she gets over it and works fine for another couple thousand miles, more or less. This has been occuring off and on for the last 20,000 miles or so.
To date, I have cleaned the TPS, then replaced the TPS with a rheostat (as suggested in several threads) and changed the brake light switch (that did fix the cruise control kicking out when hitting a bump, but not the shifting problem). The problem remains. One time when it was messing up, I stopped alongside the road and shut the ignition off and restarted it, took off and everything was fine, another time that didn't work, but it did eventually "fix" itself again, as always, while driving.
My wife wants me to take it to a shop and replace the tranny. I would do that if I felt assured it would fix the problem, but I have a funny feeling that it won't.
Any suggestions would be appreciated.

Cougsfan

OK, if no one has any suggestions, can I get an opinion if this problem would get corrected with a tranny replacement?

patdaly

Isn't your transmission........ As for the cause, there are more fixes than politicians have promises.....

It literally can be anything from Alternator noise to bad grounds..... But if it works sometimes, the mechanical portion of the thing is OK.

Cougsfan

Thanks Pat, I had the feeling I could be wasting a lot of money by changing out the tranny. Nice to hear someone confirm it. And I understand that intermittent electrical problems be very hard to diagnose and can frustrate even the best mechanics, yet alone an average one like me.
But I do need to somehow fix this. It is not acceptable to be stuck on a freeway, 100 miles away from home, and the engine is screaming it's guts out just to do 50 mph. I would hate to even sell this truck and dump the problem on a new owner 3 months down the road. (anyhow, I otherwise love the truck, would hate to sell it)
Is there a schematic or description somewhere of how the shift control works and all the components involved so I can at least scratch my head somewhat more intelligently? I will search threads on alternator noise to see how to diagnose and correct that. Bad grounds.... I wouldn't even know where to start looking.

patdaly

OD control is easy cheesy, you have constant 12V to the solenoid packs and the PCM drags it to ground to engage. Theoretically, you could add a flip switch to the ground from the tranny plug and manually drag it in when it is acting up. ( same for TC LU )

This thread gives you the pinouts for the circuit, 6 and 7 are the ones you would use ( pin 6 is OD )

https://www.dieseltruckresource.com/...d.php?t=310819

Cougsfan

Thanks again Pat, that helps takes some of the mystery out of this. I will digest what you said and study that link.

The way I think the tranny works; it is a 3 speed plus an overdrive (essential acts the same as a 4 speed because overdrive doesn't ever engage in first or second gear)

When this guy is acting up, sometimes it does momentarily downshift out of overdrive at 50-60 mph with no load and at constant speed. And I assume that the final upshift that under normal circumstances occurs in this truck at 45 to 47 mph (the shift it sometimes fails to make at all) is from 3rd into 3rd w/overdrive. If that is correct, it does indeed sound like the OD solenoid signal is not grounding or momentarily losing it's ground at times for some reason. Does that grounding occur internally within the PCM? Might it be the solenoid itself failing?

Where is that tranny plug that you mention? It would be worth looking at the connections there. Sounds like a manually controlled ground switch might be a reasonable thing to do for an emergency temporary fix.

patdaly

Yep, essentially a good old 727 with and OD unit stuck on the rear ( and a lock up TQ up front )


45 to 47 sounds about right, it has been a few years since I drove an auto equipped one, but the way mine shifted was 1-2-3-TQLU-ODLU. The Torque Converter dropped more RPM's than the OD shift did.

Yes, the PCM drags it to ground internally. Probably not a solenoid failing, they tend to either work or not. It could be an intermittent at the plug or wiring though.

Here is a picture, drivers side of trans, and yes, sometimes it can be as simple as gunk in the connector.



One other thing, I don't know how long you intend to own this truck, or how intense your love of the Cummins is, but for 95 percent of us, obtaining a service manual is almost a requirement, if nothing else than to keep some dimwit "expert" diesel mechanic from messing up your truck.

Genos garage has factory service manuals on CD for 35 bucks, I personally like the CD version over the printed ( I have both ) because I can zip right to the section I need, and print out the pages that are relevant without dragging the whole manual out and getting it greasy. I also keep a copy on the memory card on my phone ( and on a memory stick in the truck, I like redundancy ), so wherever I am, all I need is a computer and a USB cable.... If I ever do get a smart phone, it will be on there all the time, thus no need for a computer to view it.

http://www.genosgarage.com/1996-DODG.../#.VASW4aMynf0

Robert Rausch

I had some crazy symptoms with my 47RH last Spring. In and out of lockup. In and out of O.D., no O.D., then it would work fine. Then no OD above 60. Next day it was fine. Then it wasn't. I was tearing my hair out. Finally I bypassed the darn temp sensing unit in the trans line with a tiny electronic resistor which supplied the correct number of ohms to the system and I've never had a problem since then.

(edit) Yes, I used a 1,000 ohm resistor too. Now I also have a trans temp gauge, so the trans temp sensor is not needed.

Cougsfan

Actually Pat, I do have that manual. I read the transmission section a year or two ago and it seemed to aim me down a lot of rabbit trails concerning things I didn't understand or were beyond me. Some of it's nonchalant suggestions for correction for this problem are still beyond what I would be willing to do such as "Disassemble overdrive and repair as needed"

One nice feature that a forum has that a manual doesn't; you can ask the people of a forum questions (manuals don't deal too well with questions). The feedback you get is based on practical experience, rather than the long un-prioritized list of factory CYA suggestions that you get in a manual. (Don't get me wrong, the manual can be a wonderful tool too)

Because of your last comment, I got the manual out tonight and re-read the transmission section. With just the few answers that you have provided, the whole section on the overdrive function makes much more sense now, and it is far less intimidating. I have the confidence I can at least try some things now where I didn't before.

With that said. Thanks so much, Pat. Without your comment, I wouldn't have re-read the manual on this subject.

Robert, thanks for the input. As I was reading the manual, I kept your comments on the temp sending unit in mind. That sounded like it could definitely be a possible culprit. It says that if the temp sending unit is keeping it from shifting, or causing it to downshift, it will also turn the "OD off" light on. My "OD off" light stays off when it downshifts which makes me think the temp sending unit isn't my particular problem. I assume your light came on. Also, my TC lock-up has always seemed to work OK.

Alternator noise is still a potential source for problem that I have heard mentioned that I still need to understand more about. (not mentioned in the manual, by the way)

patdaly

No problem man, that's what we are here for.

And yea, this place has saved my bacon far more than I have been able to help others!

If something doesn't make sense, hop right in, we all either have had the same questions at one point or the other, or will at some point.

One thing to bear in mind is Robert has a 1995, which was the last year of the hydraulically controlled 47, so his transmission control functions might be different than the 96 up 47RE. I do not know that for a fact, but with the additional electronic control over the trans ( Governor pressure control ), it makes sense that other things might not act exactly the same. If you want to eliminate it as a possibility, a simple 1K Ohm resistor would prove it. ( 2000 and newer use a 2K resistor )

As for Alt. noise, you wouldn't expect the factory to admit they have noise....... But yea, sometimes simply wrapping the lead wire in tinfoil clears up the issue.

Alfdude1

I had a similar problem with my 1996 TCD and 47RE trans. I replaced the TPS and the problem went away. Now I have intermittent delayed 3-4 upshifts and TC lockup. Disconnected the alternate rand it seemed to shift fine. Just got my DTT noise filter yesterday and will install it this week to see if it is alternator noise.

patdaly

Alf, if that doesn't do it, take it to your local Catholic priest and have them do an Exorcism....... Just kidding ( sort of ), keep after it, there are seemingly a gazillion reasons for it to act up, and you just have to keep pursuing the solution till you get it.

Alfdude1

Just finished installing the DTT noise filter and PCM ground strap. Pretty easy install. Took it out for a test drive and not sure if it is fixed. At what speeds (approximate) does the 47RE shift into OD and TC lock up? I know it varies according to throttle position, load and acceleration. Right now under light acceleration it goes into OD around 45 mph and under a harder acceleration around 55 mph. It has been so long with the shifting issues, I don't remember what it did new.

patdaly

That sounds about right.

Alfdude1

Still trying to diagnose the transmission shifting (OD & TC).

There seems to be no rhyme or reason as to when the transmission decides to shift into OD. Sometimes @ 35mph, sometimes @ 45 and other times @ 50 mph. Sometimes if I let off the throttle completely, it will shift into OD. Once in OD it stays. I installed two LEDs that register the ground signals from the PCM for OD and TC lockup and they both light up when driving OD 1st and TC later. I contacted DTT (I have their valve body installed) and was told to adjust the TPS to 0.9vdc and it still acts the same (replaced the TPS approx 10K ago). I have installed the DTT noise filter with no change. Just had the transmission serviced with no difference.

Any other ideas? I'm going crazy.

Mike